Conventionally, input display devices having a display device on which an input device such as a touch panel lies have been widely used. An example of the touch panel includes a resistive touch panel, a capacitance touch panel, and an optical sensor built-in LCD including optical sensors in pixels of a displaying section thereof.
One of such input display devices is an input display device whose screen is to be used in a horizontal position such as a table-type input display device provided with a screen on its table. In the input display device whose screen is used in a horizontal position, a display direction (direction of an image to be displayed) is changed in accordance with a position of a user relative to the input display device. Previously, various techniques have been proposed as a technique for controlling the display direction by specifying a position of a user.
For example, Patent Literature 1 proposes a technique for controlling a display direction by providing an infrared sensor to a table-type input display device and detecting a user by the infrared sensor so that an image is displayed in a normal direction for the user thus detected.
Patent Literature 2 proposes a technique for determining a display direction by providing sensors at four corners of a screen of an information terminal device and sensing that one of the sensors is touched with a pen. Further, Patent Literature 2 also proposes a technique for determining a display direction suitable for a screen. In the technique of Patent Literature 2, when a display device is powered on, a screen split into four sections is displayed. The four sections are directed to different four directions. One of the four sections is selected by touching the one of the four sections, thereby determining in which one of the display direction the display device should display the screen.
Patent Literature 3 proposes a technique for determining a display direction corresponding to an eye direction of a user. The eye direction of the user is determined in accordance with positions of the user and a pen tip input, which positions are detected by detecting the user by the sensors provided around a table which includes a screen.
On the other hand, Patent Literatures 4 and 5 propose techniques, though which techniques are not a technique for controlling a display direction by specifying a position of a user, for removing an input by touching a screen with a palm other than an intended input by touching a screen with a pen or a finger in a case where a plurality of inputs due to an incorrect input caused by touching a palm on a screen were detected. Specifically, in consideration of a difference between an area of an input by touching a screen with a palm and an area of an input with a pen or a finger, an input having a minimum area is considered to be valid and an input by touching a screen with a palm is considered to be invalid.